Synthesis, characterization and non-enzymatic lactate sensing performance investigation of mesoporous copper oxide (CuO) using inverse micelle method

Lactate biosensors based on enzymes have been widely studied. However, they have limitations including low reliability, owing to biological degradation, and high cost. Therefore, transition metal oxides have been extensively investigated for non-enzymatic biosensors owing to their electrochemical catalytic properties and good stability. In this study, we synthesized mesoporous copper oxides (CuOs) by the inverse micelle sol-gel process and fabricated a lactate biosensor using mesoporous CuOs as the electrode material. It is difficult to synthesize mesoporous CuO using the inverse micelle method because Cu has more polymeric hydrolysis species under the same condition than other transition metals. Therefore, we controlled the formation of the polymeric hydrolysis species by setting the precursor and acid concentrations. The primary phase of copper oxalate hydrate was synthesized, and phase transformation to CuO with mesoporosity was achieved through heat treatment. The characteristics of the mesoporous CuO were analyzed by X-ray diffraction, N₂ sorption isotherms, and transmission electron microscopy. Mesoporous CuO with a large specific surface area of 166.03 m²/g was successfully synthesized after heat treatment at 250 °C. The non-enzymatic lactate sensing characteristics were assessed using an amperometric response with a three-electrode system. The mesoporous CuO-based biosensor exhibited a maximum sensitivity of 80.33 μA/mM.